It’s possible to run Morrowind in full screen mode on Windows 10, even if you’re using a screen whose resolution isn’t listed in the Morrowind video options.

To run Morrowind in full screen mode, launch Morrowind and press ESC once in the game. Click options, then video, then change the resolution to something different (anything will do). Morrowind will then turn into full screen mode. Unfortunately you have to do this each time you start playing Morrowind.